Method for improving the odor and color of tar acids



Patented Aug. 20, 1935 ui so STATE METHOD FOR IMPROVING 'rnn'onoa AND coma or TAR Aoios AENT OFFICE Carl E. Hartwig, Bayonne, N. J., assignor to The tion of New Jersey Barrett Company, New York, N. Y., a corpora- I No Drawing. -Application August 31 1932,

a Serial No. 631,275 7 x '12 oi-mi s. (01. 260- 154) This invention relates to the purification of tar acids and more particularly to a process for removmg objectionable odors from and improving the'color stability of tar acids.

By tar acids as used in this specification, I mean the organic cyclic hydroxy compounds (for: example phenol, the cresols, the xylenols) resulting from the destructive distillation of organic matter'such as bituminous coal, which 21 form salts with caustic soda and are capable of being extracted from solution in organic solvents by means of aqueous caustic soda or other aqueous'alkaline solutions. By carbolate or carbolatesolution I mean the solution of reaction products" obtained by treating free-tar acids or free-tar-acid-bearing"material with aqueous a1 kaline solutions, especially caustic soda solution. carbolate solutionscontain as solute chiefly sodium (or other metal, e. g), potassium) salts of ;.tar acid's. The term tar acids "is used in the 30;, widely claims' in a comprehensive sense and is intended t'o-includ'e tar acids whether free or in combination asimetal salts. 4

It is customary to recover tar acids for taracid-containing oils by 'treatin'g such oils with 'anaqueous'alkaline solution; these oils may be condensates obtained from the distillation of coal tar or of other tabacid-producing"material; Such oils; commonly called carbolic oils, vary in tar acid content, depending on their source. Carbolic oils resulting from by-product coke-oven operation ordinarily contain from 7 to"35 per cent byvolume of tar acids, but wide variations from this range may occur. Caustic sodais ordinarily employed for the extraction,

although other alkaline materials such as caustic potash .or theiraqueous'solutions may be employed. The solution of the sodium salts of taracids (i. e.,=the carbolate solution) isseparated from the oiL-preferably diluted with water' and distilled with steam' toremove neutral hydrocarbon material which dissolves in the caustic solution in appreciable amounts. The tar-acid content of such carbolate solutions will vary with completeness of extraction of the oil, strength of caustic solution'used, and other factors. Comme'rcial vcarbolates, before distillation with steam, V

' may contain tar acid'salts equivalent to about to 80 per cent by volume of tar acids. The carbolate solution, freed of neutral oil by steam distillation or evaporation, is treated withan acid such as sulfuric acid or with carbon dioxide, or with an acid salt such as sodium acid sulfate, 'sodium bicarbonate or the like, to. liberate the o5, ta'r acids, which float as an oilylayer on the theacids or make them worthless for manypur- 1o poses. i

It has been proposed to purify tar-acid-bearing oils (but'not carbolates) by distilling such oils in the presence of non-acidic ferric com-' pounds, such as ferric soaps, and collecting the distillate which constitutes the desired purified tar-acid -bearing oil. The explanation advanced for the alleged efiectiveness of this process to remove color-producing bodies is that the dis tillati'on of the oils in the presence of the ferric compounds results in the oxidation of dihydric tar-acid impurities (the color-forming bodies) contained in the tar acidoils into black waterinsoluble non-volatile compounds, permitting the recovery by distillation of a distillate substantially free'of such color-forming bodies.

It is an object of my invention to provide a process for treating tar acids which results in substantiallycomplete removal of such objectionable odor-forming bodies and also results in the production of tar acids of improved color stability; The process of this invention may be carried out without seriously interfering with the ordinary routine of tar acid production and requires comparatively simple and inexpensive equipment for its practice.

In carrying out my invention I treat the carbolate' solution, preferably after dilution and removal of the neutral oil by steam distillation as described above, with a small amount of a col- 4o loidal or gelatinous hydroxideiof a heavy metal.

I prefer to use iron hydroxide, either ferric or ferrous hydroxide or a combination of these because these hydroxides are cheap and effective, but other metals may be used such as the hydroxides of nickel, cobalt, chromium, copper or manganese. It will be noted that the specific gravities of each of the metals'mentioned in the preceding senalkali insoluble hydroxides of heavy tence exceeds 4. In the claims the reference to a gelatinous hydroxide of a heavy metal is intended to refer to ad hydroxide of a metal such as those enumerated which have a specific gravity of at least 4. The amount of hydroxide employed may vary from about 1 to 25 per cent by erably about. 2 percent by weight iron hydroxide,

based on the tar acid content of the carbolate,

may be used'to obtain efiective purification, and

'I may useup to about 25 per cent. It is desirable to heat the carbolate to a ter'nperature oi, say, 150 to 9 Cfbefore adding the. gelatinous material. V n s V [The-process may;conveniently be carried out by adding the required amount of almetal hydroxide previously prepared (as by theflpre'cipi-l I tation'of a'solution of 'metallic salt with an a1- kali) to the carbolate solutionfag'itating the fone-half hour,

mixture for, say, 15 minute's-Ito allowing the hydroxide to settle, separating the carbolate from the hydroxide and liberating..the

vtar acids by acidification. Instead of the above, the hydroxide maybe precipitated in the carbolate by adding thereto a solution-containing soluble metal salt such as ferric sulphate, advantage being taken of the alkaline nature .pofgthe carbolate to effect precipitation of the'metalhy- .droxide fromthe solution of the soluble metal salt. The latter procedure 'ispreferred since the, metallic hydroxide whenprecipitated in situ ape pears to be in a'more active form, ;The mixture of metalsalt solution and. carbolate may betagie; hour, thehydroxide tated for-15 minutes to permitted: to. settle and. the carbolate. then, separated from the hydroxide by filtering and wash,-

ingp; The carbolate; may beacidified to convert the-tar facid salts. to acids-and rectified bydis tillation-in-vacuoi The following is. given asian example ot-the;

practice; of: this invention;

luted' and freed from dissolved withste'a'mx to produce a carbolate; substantially free: of, neutral. oil 1 and .containing .salts of" tar acids. equivalent to "about. 20 percent by volume; of tar-acids based on the .volumelof solution; The residue of this distillation, consisted :forfthemost; part of a solution of thesodiumsalts of tar acids, the salts. of phenol, the .cresols and the xylenols predominating. To 200 cm-of, this -car-,

bolate solutionwere added 20 cc. of. a;10 percent aqueous solution of ferric sulphate (the amount of solution: added being equivalent to the addi tion of12gramsofferric sulphate); Thecarbo late was heatedto a temperatureof alziout 90?- prior to the addition 'ofnthesferric, sulphate and the mixture agitated and warmed minutes to hour. to settle for approximately 60 minutesand separated from the solution; -1'I?he carbolate was then acidified. 1 v

, In anothrzexa'mpleJZO cciz ofiai- 16% aqueous solution of. ferrous. sulfaterithe amountof solu-;

tion being equivalentto the addition of 2 grams of ferrous sulfate), were added to"200 ;cc. of. the. carbolatesolution'and otherwise the steps of Example 1 were-duplicated; I

1 -'=In afurther example-of-theinvention, 2 grams of ferric hydroxide! were added-to 200 cc; of-carr' bolatesolutions 8.1352, temperatureof about 90 C. The-mixture wasiagitated for, approximately minutesto /2 hour whileiwarming. {It was then allowed to settle for approximately: 60 minutes and the carbolate.separatedffrom the hydroxide byfiltering The carbolate was then, acidified. E The-tar acids resulting from theprocess ascarried out-inthe aboveexamples,wereondistilla I /pounds, sulfur'compounds, and traces of arsenic compoundsby the gelatinous materials used in for'about '15 The precipitate was allowed p 2,011,633 weightof thetar acids treated. In the case of .ironhydroxide, at least 1 per cent, but preftion under vacuum,,substantially free of disagreeable odor, of improved color stability, and

of enhanced value for many purposes. While the cause for the improvement in odor and increased purityof tar acids resulting from the practice of the method of the invention is not definitely known, it app ars probable that these-results areidue to the adsorption=of objec- "ti onable impurities suchas dihydroxy comtreatingthe'carbolates. l I

Without departing from the scope of my invention I may treat with-the reagents described not only carbolate formed by extracting" tar-acidcontaining oil, but also carbolate formed by dissolving. impure tar acids in caustic soda or other alkaline solutions, or produced in any other way.

The terrnfiron hydroxide as used'in the specificationand. claims includes both ferrous and ferric hydroxides; .1

While I-have described apreferred method'oi carrying out my invention, .I. do':not Wish my inonlyas limited by the following claims; I claim:, r A

vention to be considered as; limited thereby; but;

1.- In thesprocess of purif ying tar .acidsiwhich comprises dissolving'tar. acids in an:alkaline so.- lution; to form. a icarbolate solution; the step which comprises treating the carbolate solution. with a gelatinous hydroxide of"-a :heav'y metal which hydroxide is insolublein alkali,

.2. In thegprocess'of'purifying tar acids "which comprises dissolving tar acids in an alkaline solution to form a I carbolate solution}. the. step with iron hydroxide. 1

which hydroxide is formed by precipitation in the:

carbolate s'olution.

4. .In: the process. of purifying tanacids which 4 comprises dissolving gtar acids in an'alkaline, so-

lution "to form vacarbolate.solution,- pthe,rstep which comprisestreating a carbolate; solution with iron hydroxideprecipitatedin the carbolic solution.- r Y 5. The process for "purifying tar acids'which,

comprises dissolving tar acids in a;sclution of an alkaline material, whereby a carbolate solution is formed,-agitating said carbolate solution with 'carbolatelsolution.

v3. -In the process of purifying tar acids which.

the: step I'sjolution I a-gelatinous hydroxide of aheavy metal,-separating the carbolate solution from the meta1;hydrox-. idle and liberating tar acids :from the separated- The process for purifying ;tar.g acids which comprises dissolving tar acids Iin' a 1' solution of a l alkaline-materialwhereby a carbolate solution is formed,=agitating; said carbolate solution with iron hydroxide, separating, the carbolate solution'from the iron hydroxide and liberatingtar acids from theseparated carbolate solution; 7" I '7. In the processof' purifyingitar acids. the step which comprises "treating carbolate solution Y withat-least 1 per cent byweight iron hydroxide,v based;.-on the tar acid content-of the car-.- bolate solution'r 8. In-the process of purifying tar acids, the stepwhichcomprises.forminggin situ a gelatinous-metalhydroxide precipitate. I In, the process of recovering tar acidsfrom tar-acid-ibe'aringoils, the combination of steps 35 I whichcomprises'treatingthe carbolate'solution i which comprise extracting tar-acid-bearing oils with an aqueous alkaline solution whereby a carbolate solution is formed, agitating said carbolate solution with gelatinous iron hydroxide, separating the carbolate solution from the iron hydroxide and liberating tar acids from the separated carbolate solution.

10. In the process of producing combination of steps which comprise heating a carbolate solution containing said tar acids as alkali metal salts, adding to the carbolate solution a solution of ferric sulphate equivalent as ferric hydroxide to at least 1 per cent of the weight of the tar acids present in the carbolate,

tar acids the whereby gelatinous iron hydroxide is precipitated, agitating the carbolate solution while in contact with said iron hydroxide at an elevated temperature, separating the carbolate solution from the precipitated iron hydroxide and recovering tar acid from the carbolate solution.

11. The method of purifying tar acids, which comprises contacting the tar acids with a gelatinous iron hydroxide.

12. The method oipurifying tar acids which comprises contacting the tar acids with a gelatinous metal hydroxide.

CARL E. HARTWIG. 

